HygroSet DHYG-FM Adjustable Digital Hygrometer for Front Mount Humidor. An essential accessory for every cigar humidor. It has the same great adjustment features as the HygroSet I and II but is made specifically for exterior front mount humidors. The HygroSet FM is capable of being adjusted after calibration. Each click of the adjustment knob changes the humidity display (+/-) by 1%. This practical hygrometer has a 10-second refresh rate, makes it easy to use. Button cell battery included in the set.